1. Field of the Invention
The present invention relates generally to a laser beam projection apparatus employed in the sector of construction and civil engineering and, more particularly, to a laser beam projection apparatus used for level surveying using a laser beam and a work of marking along a horizontal or perpendicular surface.
2. Related Background Art
There is known a laser beam projection instrument as disclosed in, e.g., U.S. Pat. No. 4,221,483. This laser beam projection instrument includes an optical system having a collimator lens which substantially collimates the laser beams emitted from a light source such as an He--Ne gas laser or a laser diode. The thus collimated laser beams are then emitted in the horizontal direction via a rotary mirror. Thus, the laser beam projection instrument supplies the laser beams swept on the horizontal plane.
This type of conventional laser beam projection instrument is placed substantially at the center of a room, and the swept laser beams are emitted, thereby making it possible to perform leveling on an inner wall surface. That is, if the laser beams are visible, a line of the laser beam appears on the peripheral wall surface, and, therefore, the worker puts a mark on the center of the line width. Whereas if invisible, a dedicated sensor is mounted on the wall surface, and the marking may be effected. Such a marking operation is executed at a predetermined interval along the line of laser beams, and thereafter the respective marks are connected by a line, thus completing the leveling operation.
Further, as disclosed in U.S. Pat. No. 4,830,489, there is also known an alignment apparatus using the laser beam projection instrument in combination with one or a plurality of sensors.
If a distance from the laser beam projection instrument to the wall surface or the sensor is long, however, a width of the laser beams emitted from the conventional laser beam projection instrument is gradually expanded. Consequently, there arises a problem in which the line of the laser beams becomes thick enough to induce a deterioration in terms of a marking accuracy. Further, in the case of the visible laser beams, there is caused such a problem that a luminance on the wall surface decreases with the expansion of the beam width or an increase in a beam shifting speed on the wall surface, resulting in a worsened visual recognizability.
Hitherto, there has been also proposed a laser beam projection instrument incorporating a function of manually control the optical system so that the laser beams are converged on an object such as a wall surface or the like. There exists, however, a problem in which two workers are needed for controlling the optical system and for confirming the width of the laser beams on the wall surface, and, besides, the work is conducted while the two workers communicated with each other, resulting in a worsened workability.